Project Summary The exact pathogenetic process that triggers neurodegeneration in ALS is currently unknown, but it is likely to be multifactorial, as for other neurodegenerative diseases. Recently, growing attention has been focused on events related to innate and adaptive immune responses, and there is increasing evidence of a significant involvement of inflammatory and immune pathways in the disease. However, their exact cellular identity, molecular and functional phenotypes, and their protective or detrimental roles in ALS progression are poorly understood. We previously found that both peripheral Ly6CHi monocytes in SOD1 mice and their analogous CD14+/CD16? monocytes from ALS patients express proinflammatory profiles. These studies lead us to begin a series of investigations to define markers of disease onset and progression in ALS. We started a prospective, longitudinal study collecting detailed clinical information, peripheral blood mononuclear cells (PBMCs) and plasma from people with ALS. Two cohorts of ALS subjects, sporadic (sALS) and familial (fALS), are followed up in time, from early until the late stages of the disease. The proposed project will identify the micro-RNA and proteomic signatures in blood-derived inflammatory monocytes and plasma in ALS. In Aim 1, we will investigate miRNA and proteomic changes in blood CD14+/CD16? monocytes and plasma from the onset and during disease progression of sALS and fALS (with SOD1 or C9orf72 gene mutations). The Aim design allows a comparative analysis of miRNA and protein expression in multiple dimensions utilizing 1) small RNA-seq to compare temporal changes of miRNAs expression within the ALS and healthy controls; 2) correlated clinical information in the variability over the time course; and 3) Integrated network data analysis between miRNA and proteomics. We leverage our unique longitudinal collection of sALS and fALS for which we have multipoint blood draws during their disease progression In Aim 2, we will characterize and validate the main hits in an independent validation cohort of ALS subjects. Acknowledging that the biomarker discovery in any field suffers from lack of replication, we believe that replication of our findings in an independent cohort is of highest importance. The independent replication, along with the validation of the main hits using different technologies will identify only robust potential biomarkers to further test for clinical utility.